Bases Butylmagnesium bromide

Asymmetric synthesis of fi-hydroxy carboxylic estersEsters of 1 in the presence of f-butylmagnesium bromide as base react with aldehydes and ketones to form optically active a-sulfinyl-jS-hydroxy carboxylic esters, which are desulfurized by aluminum amalgam in aqueous THF (equation I). Chemical yields are 75% of... 

One of the first detailed studies on these systems was that of Beaman (26), who showed that methacrylonitrile polymerizes by an anionic chain mechanism when treated with various bases, including Na in liquid ammonia at —75° C. He noted also that low molecular weight polymers are obtained from reaction of acrylonitrile with butylmagnesium bromide. Foster (56) extended the liquid ammonia method to copolymerization studies in which acrylonitrile was combined with styrene, with methyl methacrylate and with vinyl butyl sulfone. Satisfactory data were obtained only with the sulfone, in which case there was some tendency for alternation. 

Aldol-Type Addition. Aldol-type addition of the magnesium enolate of (R)-(+)-7-butyl 2-(p-tolylsulfinyl)acetate, prepared with 7-butylmagnesium bromide, with aldehydes and ketones afforded, after desulfurization with Aluminum Amalgam, p-hydroxy esters in very high diastereoselectivity (eq Two chiral centers are created in the first step with very high diastereoselectivity (mainly one diastereomer is formed). A model M based on the structure of the sulfinyl ester enolate (determined by C NMR) and on electrophilic assistance of magnesium to the carbonyl approach, was proposed to explain and predict the absolute configuration of the two created chiral centers. ... 

Aldol-Type Condensation. The aldol-type condensation of the enolate anion of sulfinylpropionate, which was prepared as usual with the base t-butylmagnesium bromide, with aldehydes afforded after desulfurization with Aluminum Amalgam the corresponding 3-hydroxy esters in high yield (90%) and, with aliphatic aldehydes, high diastereoselectivity (eq 3). The amount of asymmetric induction was determined by transformation of the 3-hydroxy esters to the corresponding isopropyl-substituted alcohols. 

For example, when r-butylmagnesium bromide is the base, the diastereomeric ratio of the adducts... 

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